JP4152006B2 - Terminal forming jig - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board on which an integrated circuit chip is mounted, and a jig for forming metal column terminals on the wiring board and a printed board.
[0002]
[Prior art]
As a terminal provided for connecting a wiring board to another wiring board, a lead, a pin, a ball-like terminal or the like is known. A wiring board provided with pins in a grid shape on a wiring board body is a PGA type wiring. A circuit board and a circuit board provided with ball-shaped terminals in a lattice shape may be called a BGA type circuit board.
[0003]
There is a PGA type wiring board called a butt joint PGA type wiring board in which the tips of pins are soldered while being abutted against mounting pads provided on another wiring board to connect the two.
[0004]
FIG. 7A shows an example in which the BGA type wiring substrate 100 is connected to the printed circuit board 120. In the upper surface (first surface) 101a of the wiring substrate main body 101 mainly composed of alumina ceramic, An integrated circuit chip (hereinafter also simply referred to as an IC chip) 111 made of Si is mounted. Specifically, Pb 95% -Sn 5% high-temperature solder is formed between the IC connection pads 112 formed on the lower surface 111b of the IC chip 111 and the chip connection pads 104 formed on the upper surface 101a of the wiring board body 101. They are connected by a flip chip method, which is connected by solder bumps 113.
[0005]
On the other hand, the printed circuit board 120 includes a printed circuit board main body 121 made of a glass-epoxy resin composite material (JIS: FR-4) and a mounting pad 122 made of copper formed on the upper surface 121a. Are connected by eutectic solder balls 103 welded to the surface metal layer 102 formed on the lower surface (second surface) 101b.
[0006]
In such a connection body of the BGA type wiring board 100 and the printed board 120, the direction along the second surface 101 b on the solder ball 103 due to the difference in thermal expansion coefficient between the wiring board main body 101 and the printed board main body 121 (see FIG. (Middle / left / right direction) shear stress is applied. Spherical solder balls are easy to form, but the height and maximum diameter are almost the same, and if the pitch (interval) made of solder balls is to be narrowed, the distance between the BGA type wiring board main body and the printed board 100 becomes small. . For this reason, due to repeated thermal stress, there is a problem that breakage occurs as indicated by a broken line, particularly near the surface metal layer 102 of the solder ball 103 on the outer peripheral side.
[0007]
On the other hand, in the pad joint PGA type wiring board 200 shown in FIG. 7B, the IC connection pads 212 formed on the lower surface 211b of the IC chip 211 and the upper surface 201a of the wiring board main body 201 are similar to the above. The chip connection pads 204 formed are flip-chip connected by solder bumps 213 .
[0008]
On the other hand, the connection with the printed circuit board 220 is performed by connecting the tip (lower end in the drawing) of the Kovar pin 203 connected to the connection pad 202 on the second surface (lower surface) 201b by a silver solder (not shown) to the printed circuit board body 221. This is abutted against the mounting pad 222 formed on the upper surface 221a and soldered by the eutectic solder 205.
[0009]
When connected by such a bad joint, since the pin 203 bends and absorbs the shear stress in the direction along the second surface 201b (the left-right direction in the figure), the connection is difficult to break and highly reliable. be able to.
[0010]
[Problems to be solved by the invention]
However, in this butt-joint PGA type wiring board 200, it is necessary to connect a large number of minute pins 203, sometimes hundreds to thousands, to the wiring board body 201 in advance by silver solder or the like. Costs and processes are required, and costs are high.
[0011]
Further, since the diameter of the tip of the pin 203 is thin, even if a positional shift occurs when the eutectic solder 205 is melted, the surface area of the eutectic solder 205 hardly changes. Therefore, unlike the solder ball connection, the self-alignment effect hardly occurs. For this reason, it is necessary to perform positioning when connecting the wiring board 200 and the printed board 220 with high accuracy.
[0012]
In the above description, the case where the wiring board main body mainly composed of alumina ceramic is used has been described. However, when the wiring board main body 301 is made of a material containing a resin such as a glass-epoxy resin composite material, the IC chip 311 to be mounted on the upper surface (first surface) is made of Si, so the coefficient of thermal expansion is small ( α = 3 to 4 × 10 ⁻⁶ / ° C.) and 10 to several 10 × 10 ⁻⁶ / ° C. Furthermore, since the material containing resin is softer (less rigid) than ceramic or the like, for example, as shown in FIG. 8A, the region where the IC chip 311 is mounted becomes convex downward when heated. Each solder ball 303 is subjected to a stress that expands and contracts up and down as it tries to warp and deform. Note that the deformation shown in FIG. 8A greatly emphasizes the deformation amount. Actually, since the eutectic solder balls 303 are difficult to deform, the amount of deformation is very small. For this reason, the stress causing such deformation exhausts the solder ball 303, and finally, as shown in FIG. 8B, the position corresponding to the place where the IC chip 311 is mounted (the position corresponding to the IC chip). It has been found that the solder balls 303 formed in () are selectively defective as indicated by broken lines.
[0013]
The present invention has been made in view of such a problem, and absorbs deformation in a direction along the surface of the substrate caused by a difference in thermal expansion coefficient between a wiring substrate and a mounting substrate to which the wiring substrate is attached, and has high reliability. terminal can obtain sexual further provides a jig which can be manufactured with high terminal connection reliability hardly broken by vertical expansion due to warping deformation, it is an object.
[0014]
[Means for Solving the Problems]
A terminal forming jig according to the present invention (Claim 1) is for forming a metal column terminal having a height higher than the maximum diameter by welding a metal to a surface metal layer formed on one main plane of a wiring board. a terminal forming jig, and at least the outer surface is made of a material which does not wet with the weld metal, a plurality of bottomed holes having a shape corresponding to the metal column terminal is formed, it bottomed holes of the above surface metal layer which can accommodate a plurality of solder balls, the intermediate part excluding the opening and the bottom portion is substantially constant inner diameter, is deeply formed and compared to the opening diameter Rutotomoni, air vent in the bottom of the bottomed hole A small hole is formed.
[0015]
By using such a terminal forming jig, a surface metal layer provided on one main plane of the wiring board while forming a plurality of molten solder balls into a metal column terminal having a shape higher than the maximum diameter. It can be fixed to. That is, it is possible to prevent the molten solder ball from being deformed into a spherical shape or a hemispherical shape due to surface tension or the like, and to form a metal column terminal having a height higher than the maximum diameter. And since the said bottomed hole is a magnitude | size which can accommodate the corresponding surface metal layer in the opening part, the said metal column terminal can be reliably formed on the said surface metal layer. Furthermore, even when a plurality of terminals are arranged on one main plane of the wiring board, a large number of metal column terminals can be easily formed at a time.
In addition, since a small hole for venting air is formed at the bottom of the bottomed hole, when the solder ball for forming the metal column terminal is filled, heated and melted, the air in the bottomed hole And newly generated gas can be easily released. Therefore, it is possible to prevent a situation in which such air or the like is trapped in the bottomed hole and forcibly escapes from the opening, causing an explosion or the like, swelling to the metal column terminal, void, or destruction. it can. In addition, since the bottomed hole is deeper than the opening diameter, the above-described problem is likely to occur when there is no small hole for venting air, which is beneficial.
[0016]
The material of the jig used in the present invention may be any material that has heat resistance and does not wet the molten metal. Specific examples include graphite and stainless steel. When graphite is used, a graphite material (for example, 1.2 or less) having a low anisotropic coefficient of thermal expansion coefficient is optimal. The jig is preferably made of a material that does not get wet with the molten metal that forms the metal column terminal, but at least the surface (upper surface, inner surface of the bottomed hole, etc.) does not get wet with the metal. It only has to be made.
[0017]
The material of the main body portion of the wiring board may be selected from materials that can withstand heat when connected to the mounting board and that do not break even when subjected to stress due to differences in thermal expansion coefficient with the mounting board. . In order to reduce the generated thermal stress, in consideration of the material of the IC chip and the mounting substrate, a material having a thermal expansion equivalent to or intermediate between the material of the IC chip and the mounting substrate is appropriate. Specifically, ceramics such as alumina, mullite, and aluminum nitride, resins such as epoxy, polyimide, BT, and polyurethane, composite materials of these resins and fibers such as glass and polyester, and composite materials of these resins and ceramic powder Etc.
[0018]
The wiring board targeted by the present invention is interposed between the electronic component mounting wiring board and the mounting board in addition to the electronic component mounting wiring board for mounting electronic components such as IC chips, It also includes a relay wiring board used to connect the two.
In addition, examples of the metal material for forming the metal column terminal include lead (Pb), tin (Sn), zinc (Zn), and alloys mainly composed thereof, such as Pb-Sn alloy high temperature solder (for example, Pb90% -Sn10). % Alloy, Pb95% -Sn5% alloy), Pb-Sn eutectic solder (Pb36% -Sn64% alloy), white metal, and the like. These metals are preferable as metal column terminal materials because they are relatively soft and can absorb the stress generated between the wiring board and the mounting board due to a difference in coefficient of thermal expansion. In addition, since lead, tin, and the like have a recrystallization temperature at room temperature, they are easily recrystallized even if they are plastically deformed. Therefore, even if repeated stress is applied, it does not easily break (break), which is convenient.
[0019]
Further, the metal column terminal in the present invention may be a substantially columnar shape whose height is higher than the maximum diameter, and may be a rectangular column or a triangular column in addition to the columnar shape. However, in order to avoid the stress from concentrating on the corners, a polygonal column shape is preferable, and a column shape is optimal. Thus, the shape of the bottomed holes of the terminal forming jig is also suitably selected to match the shape of the metal pole terminals to be formed. That is, in the bottomed hole, an intermediate portion excluding the opening and the bottom has a substantially constant inner diameter .
[0020]
Also, the bottom of the bottomed hole (bottom) may have any shape, even if a plane may be substantially decreased to shape such as reverse hemispherical or Ryakugyakuhan conical. When the bottom surface is flat, the metal column terminal can be easily raised by melting the solder ball and forming the metal column terminal so that the tip of the metal column terminal hits the bottom surface of the bottomed hole. Can be aligned. Further, the bottom surface of the bottomed hole may be formed by members separate from the member constituting the inner circumferential surface of such blind holes. That is, the terminal forming jig may be configured by combining a member having a through hole and a member that closes one opening of the through hole. If comprised in this way, manufacture of a terminal formation jig | tool is easy .
[0021]
The bottomed hole also includes a terminal forming jig (Claim 2) having a tapered portion at the opening thereof .
[0022]
According to the terminal formation jig of claim 2, it is possible to easily fill the bottomed holes and Handabo Le. That is, when the solder balls are filled in the bottomed holes in a paste state and melted and fixed to the surface metal layer of the wiring board to form the metal column terminals, the paste is easily filled. Become .
[0023]
Further, the present invention includes a terminal forming jig (claim 3) in which a plurality of air vent small holes are formed in the bottom of the bottomed hole.
[0024]
According to the terminal forming jig of claim 3, when the metal material for forming the metal column terminal is filled, heated and melted, air in the bottomed hole, newly generated gas, etc. are further increased. Can be released easily .
[0025]
Moreover, the bottom part of the said bottomed hole is cone shape, The terminal formation jig | tool (Claim 4) by which the said small hole is formed in the deepest part of the said bottom part is also contained in this invention . According to this, by filling the metal material for forming the metal pillar terminals, when heated and melted, a gas or the like generated air and newly bottomed hole can be reliably released.
[0026]
Furthermore, the bottomed hole is formed by a first member having a through hole that forms an inner peripheral surface of the bottomed hole, and a second member that closes the through hole and has a small hole for venting air . The terminal forming jig (Claim 5) is also included in the present invention. According to this, formation of a bottomed hole and a small hole (hole) opened to the bottom thereof can be easily performed by the two members.
[0028]
The wiring board obtained by the present invention has a metal column terminal having a height higher than the maximum diameter on the surface metal layer provided on one main plane of the wiring board main body. Deformation along the plane direction of the substrate caused by a difference in coefficient of thermal expansion from the mounting substrate can be easily absorbed, and high connection reliability can be achieved. Furthermore, since the metal column terminal is difficult to break even in the vertical expansion and contraction due to warp deformation, the wiring board is further excellent in connection reliability.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view of a carbon terminal forming jig N used in this embodiment. A bottomed hole N1 having a diameter of 0.7 mm and a depth of 1.8 mm is formed in the upper surface N3 at a position corresponding to the surface metal layer on which the metal column terminal is to be formed. The bottom N4 of the bottomed hole N1 is formed in a conical shape as shown in FIG. 2 (a), and a hole (small hole) for venting air that penetrates the terminal forming jig N downward in the deepest part. ) N2 (φ0.2mm) is formed.
[0030]
Such a terminal forming jig N is formed by drilling a bottomed hole N1 and a hole N2 by drilling a carbon plate.
Next, a method for manufacturing a wiring board having metal column terminals using the terminal forming jig will be described with reference to FIGS.
First, as shown in FIG. 3A, a carbon terminal forming jig N and a wiring board 1 are prepared. The wiring board is made of ceramic mainly composed of alumina, and a surface metal layer 2 composed of a tungsten metallized layer and a nickel plating layer is formed on the surface thereof. Solder balls D1 are placed in the recess N1 of the columnar terminal forming jig N (three pieces in FIG. 3), and a surface metal layer 2 formed on the ceramic wiring board 1 has a bottom above it. Positioning is performed so as to correspond to the hole N1, and both are overlapped (see FIG. 3B).
[0031]
Thereafter, both the main body 1 and the jig N are reversed and turned upside down, and the solder ball D1 and the surface metal layer 2 are brought into contact with each other (see FIG. 3C). If it heats and cools in this state, the metal column terminal 3 can be reliably welded to the surface metal layer 2 (refer FIG. 4). FIG. 4 is a perspective view showing the wiring board 1 on which the metal column terminals 3 are formed. Although an IC chip is mounted on the upper surface in the figure, only the IC chip connection pads 4 are shown here. And
[0033]
Further, as a different form of the terminal forming jig N used in the present embodiment, as shown in FIG. 2B, the diameter of the vicinity of the opening of the bottomed hole N1 gradually increases toward the upper surface N3. You may use what was formed so that it might become. In this case, since it has a tapered portion N5, there is a merit that it is easy Shi input projecting the Handabo Le.
[0034]
( Reference form)
Next, the terminal forming jig of the reference form will be described with reference to FIG.
Terminal forming jig M of reference embodiment shown in Figure 5, forms a diameter 0.7 mm, height (depth) 2.2 mm of the through-holes M1 at a position corresponding to the surface metal layer 2 to form a metal pillar terminal 3 This is a plate-like terminal forming jig made of stainless steel. Stainless steel is heat resistant and has the property of not easily getting wet with molten solder.
[0035]
Next, a method for forming the metal column terminal 3 using the terminal forming jig M will be described with reference to FIGS.
As shown in FIG. 6 (a), the wiring board 1 is arranged so that the surface on which the surface metal layer 2 is formed faces upward, and the through holes M1 and the surface metal layer 2 are made to correspond to each other. Then, the terminal forming jig M is placed. Further, three solder balls C each having a diameter of 0.65 mm are put into the through hole M1. Next, when the solder balls C are melted, the metal column terminals 3 are welded to the surface metal layer 2 and integrated with each other as shown in FIG. A side surface of the metal column terminal 3 follows the inner peripheral surface of the through-hole M1, and a metal column terminal having a hemispherical shape at the tip is formed by surface tension. Since each of the metal column terminals 3 is formed by melting three solder balls C having a constant diameter, the volume is constant, so that the height can be made uniform.
[0037]
(Embodiment 2 )
Further, Oite the embodiment 1, was used terminal forming jig N formed integrally, as shown in FIG. 9 (a), 2 or more of the combined terminal forming jig L member It may be used. As shown in FIG. 9A, the terminal forming jig L in Embodiment 2 includes a bottomed hole L1 having a bottom surface L2. Further, an air vent hole (small hole) L3 is formed on the bottom surface L2.
[0038]
The terminal forming jig L is composed of a first member P and a second member Q shown in FIG. That is, the first member P is formed with a through hole P1 that forms the inner surface of the bottomed hole. Further, an air vent hole L3 is formed in the second member Q. By combining the first member P and the second member Q such that the upper surface Q1 of the second member Q closes the through hole P1, a bottomed hole having a bottom surface L2 as shown in FIG. L1 is formed. By forming the terminal forming member with two members in this manner, it is easy to form the bottomed hole.
[0039]
In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied within the scope of the invention.
[Brief description of the drawings]
FIG. 1 is a front view of a terminal forming jig N according to a first embodiment.
FIG. 2 is a partially enlarged sectional view of a terminal forming jig N according to the first embodiment.
FIG. 3 is an explanatory diagram of a process of forming a metal column terminal 3 using a terminal forming jig N.
FIG. 4 is a perspective view of a wiring board 1 having metal column terminals 3;
FIG. 5 is a partially enlarged cross-sectional view of a terminal forming jig M according to a reference embodiment.
Figure 6 is an explanatory diagram of a process for forming a metal pillar terminal 3 by using the terminal forming jig M.
FIG. 7 is an explanatory view showing a state in which a wiring board on which an integrated circuit chip is mounted is connected to a printed board according to a conventional technique, and (a) is a diagram in which the wiring board and the printed board are connected by a spherical solder ball. State (b) shows a state in which the pins provided on the wiring board are abutted against the printed circuit board and connected.
FIG. 8 (a) emphasizes deformation when an integrated circuit chip is mounted and a BGA type wiring board having a wiring board body made of a resin-containing material is connected to a printed board. (B) is explanatory drawing explaining the fracture | rupture location of a connection terminal.
FIG. 9 is a partially enlarged cross-sectional view of a terminal forming jig L according to a second embodiment.
[Explanation of symbols]
N, L: terminal forming jig N1, L1: bottomed hole P1: through hole N2, L3: air (gas) vent holes (small holes)
N4, L2: Bottom D1, C: Solder ball
P: First member
Q: 2nd member 1,100,200,300: Wiring board 2,102: Surface metal layer 3: Metal pillar terminal

Claims (5)

A terminal forming jig for forming a metal column terminal having a height higher than the maximum diameter by welding a metal to a surface metal layer formed on one main plane of a wiring board,
At least the outer surface is made of a material that does not get wet with the weld metal,
A plurality of bottomed holes having a shape corresponding to the metal column terminal are formed, and the bottomed hole can accommodate the surface metal layer and a plurality of solder balls, so that an intermediate portion excluding the opening and the bottom is substantially omitted. a constant inner diameter, is deeply formed and compared to the opening diameter Rutotomoni, pores of the air vent in the bottom portion of the bottomed hole is formed,
A terminal forming jig. The bottomed hole has a tapered portion at its opening,
The terminal forming jig according to claim 1. There are a plurality of air vent small holes formed at the bottom of the bottomed hole.
The terminal forming jig according to claim 1, wherein: The bottom of the bottomed hole has a conical shape, and the small hole is formed in the deepest part of the bottom.
The terminal forming jig according to any one of claims 1 to 3, wherein the terminal forming jig is provided. The bottomed hole is formed by a first member having a through hole that forms an inner peripheral surface of the bottomed hole, and a second member that closes the through hole and has a small hole for venting air.
The terminal forming jig according to any one of claims 1 to 4, wherein the terminal forming jig is provided.

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